“…Due to their excellent microwave performances, 1 high mechanical properties, 2 adjustable coefficient of thermal expansion, 3 and possible applications in various novel fields, [4][5][6] for example, electronic packing devices, millimeter-wave dielectrics or hard disk substrates, glass ceramics in the MgO-Al 2 O 3 -SiO 2 system have been extensively studied over the past several decades. To alter the nature of exclusive surface crystallization in the stoichiometric cordierite composition (2MgOÁ2Al 2 O 3 Á 5SiO 2 ), extensive research has focused on nucleating agents, such as TiO 2 , ZrO 2 , CeO 2 , or P 2 O 5 .…”